Hi Ron, So in theory, replacing the USB2 chip with a USB3 would allow access to the full sample rate, or is there some other internal limitation?
Regards, Adrian On August 25, 2018 8:06:20 AM UTC, Ron Economos <w...@comcast.net> wrote: >The maximum Transport Stream rate of DVB-T is 31.67 Mbps, so the USB >interface only needs to deliver 4 MB/s. Since you need two 8-bit >samples >in IQ mode, it's 2 Msps. > >Ron > >On 08/25/2018 12:44 AM, Adrian Musceac wrote: >> Hi Marcus, >> >> You're right about the RTL sample rate, but I'm curious about why it >> is so small. >> Is it the bus speed? The ADC is obviously fast enough for DVB-T2. >> >> Regards, >> Adrian >> >> On August 24, 2018 7:42:17 PM UTC, "Müller, Marcus (CEL)" >> <muel...@kit.edu> wrote: >> >> Hi Martin, >> >> internally, the RTL dongles are fast enough to capture full DVB-T >(not >> -T2) channels, and demodulate, and decode them, and deliver the >video >> stream to the host. However, RTL-SDR can't use that mode - it >uses a >> "bypass the whole Digital TV specific stuff" mode and directly >passes >> IQ samples through USB. >> >> In that mode, it simply can't do more than 2 or 3 MS/s (can't >> remember), which isn't enough to cover 6 MHz - so everyone's >right, you >> can basically receive the AM black/white info at a partial >bandwidth of >> the ca 5 MHz of the luma signal, but you won't get any color >> information that way, or audio with the same receiver as you do >video. >> >> Cheers, >> Marcus >> >> On Fri, 2018-08-24 at 12:22 -0500, Martin McCormick wrote: >> >> First, I will talk about the things I know for sure. The NTSC >> analog system as well as Pal systems in a lot of the rest of >> the world had a lot in common with eachother. Both systems >> transmitted an AM video signal in Vestigial single sideband >> mode such that the carrier frequency was always about 1.25 >MHZ >> above the start of a channel. NTSC systems in the Americas >> also transmitted an audio carrier in FM which was always 4.9 >> MHZ above the video carrier. Pal systems used exactly the >same >> type of transmissions except that the 625-line video at 25 >> frames per second made a slightly wider spectrum such that >the >> audio and video carriers were separated by 5.x MHZ, making >> each Pal channel 7 or 8 MHZ wide. As others have suggested, >> you could probably get a monochrome fuzzy image if you can >get >> your sound card to sample fast enough. You can also decode >the >> mono sound by setting your RTL receiver to behave just like a >> FM broadcast receiver but set the frequency to whatever the >> video carrier frequency is plus 4.5 MHZ. if the video carrier >> is 55.250 MHZ, the audio will be at 59.75 MHZ. The deviation >> is 75 KHZ unlike FM radio which is 150 KHZ. That would be a >> good simple test to see if you are receiving the channel at >> all. I am guessing that since the RTL chips were designed for >> the European television market for cable and over-the-air >> broadcasts, they can be sampled extremely fast since the >> digital channels still take up the same bandwidth as their >> analog ancestors. Martin McCormick WB5AGZ Anders Hammarquist >> <i...@openend.se> writes: >> >> In a message of Fri, 24 Aug 2018 10:27:40 +0200, "Ralph >A. >> Schmid, dk5ras" writes: >> >> Hi Andres, just had a short look: doesn't NTSC >use >> a nearly 6 MHz bandwidth? Best regards, Marcus >> >> Yes, no way with the RTL to catch NTSC, it does in >SDR >> mode only 2.smth >> >> MHz bandwidth. Actually, you should be able to get a >> picture. The horizontal resolution will be about half of >> what it would be for the full bandwidth, and no colour >(as >> the colour subcarrier at 3.58 MHz is outside the pass >> band). You want the pass band of the reciever from just >> below the video carrier and as high as it will go. >/Anders >> >> >------------------------------------------------------------------------ >>
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